The melting temperature of a DNA molecule can be determined by differential scanning calorimetry (Impact 12.1). The following data were obtained in aqueous solutions containing the specified concentration [salt of an soluble ionic solid for a series of DNA molecules with varying base pair composition, with of the fraction of G-C base pairs:

(a) Estimate the melting temperature of a DNA molecule containing 40.0 per cent G-C base pairs in both samples. Hint. Begin by plotting Till against fraction of G-C base pairs and examining the shape of the curve.

(b) Do the data show an effect of concentration of ions in solution on the melting temperature of DNA? If so, provide a molecular interpretation for the effect you observe.

Transcribed Image Text:

f alt=1.0 x 10² mol dm 0.375 339 0.509 344 alt=0.15 mol dm³ T/K T/K 0.375 359 0.509 364 0.589 348 0.589 368 0.688 351 0.688 371 0.750 354 0.750 374